The fast activating potassium current, I(K,f), in guinea-pig inner hair cells is regulated by protein kinase A.

The mammalian inner hair cell (IHC) responds to displacements produced in the cochlea by sound by releasing neurotransmitter from its basal pole. A basolateral fast activating potassium current, called I(K,f), allows IHCs to act as sensory cells at high frequencies by shortening the membrane time constant. This current is co-expressed with a slower activating current, I(K,s). We have studied the intracellular regulation of IHC currents using the whole-cell patch clamp technique in conjunction with agents that influence the function of protein kinase A (PKA). Bath applied 8-Bromo-cAMP, an activator of PKA, increased the amplitude of outwardly rectifying currents and shortened the exponential time constant of activation. Following blockade of I(K,s) by intracellular 4-AP, I(K,f) could be reduced in amplitude by H-89, an inhibitor of PKA. Our results suggest that PKA regulates I(K,f) and so shapes the frequency response of IHCs.